I would just leave your brew alone if it's already fermenting... Don't worry, they are both going to give you the same color, but the malt will give you a slightly less bitter taste than black unmalted barley...
The primary reason you are using roast barley is to adjust the color of beer to get that reddish tone and to add dryness to the finish... it should have been a low quantity used anyways so I think you are going to brew a good batch of beer...